Obstructive Sleep Apnea (OSA) is a life-threatening condition characterized by frequent episodes in which an individual stops breathing or breathes less efficiently during sleep. OSA is caused by a blockage of the airway typically resulting from the collapse and closure of the soft tissue in the rear of the throat during sleep. With each apnea event, the brain arouses the individual in order for the individual to resume breathing, but consequently sleep is extremely fragmented and of poor quality.
According to the National Institute of Health, OSA currently affects more than twelve million Americans (4% of men and 2% of women), making this disorder as common as adult diabetes. Further, the disrupted and/or poor quality sleep that is associated with OSA may lead to serious health issues including hypertension, heart disease, diabetes, and stroke. Moreover, untreated sleep apnea may be responsible for job impairment and motor vehicle crashes. For example, the Department of Transport in the UK estimates that 20% of road accidents leading to death and serious injury are caused by drowsiness or sleep disorders.
When an individual is diagnosed with OSA, the individual may be prescribed a therapeutic regime involving the use of a Continuous Positive Airway Pressure (CPAP) device. The CPAP device works by delivering a steady flow of air through a soft, pliable mask worn over the individual's nose. The CPAP device essentially pressurizes the throat of the individual thereby preventing the collapse of the soft tissue and keeping the airways open and allowing the individual to breathe uninterrupted during sleep.
The CPAP device is both loud and uncomfortable and has met with various non-compliance issues. However, it is possible to augment the CPAP device to control gas delivery to the individual according to changes in the physiological state of the wearer. These changes can be seen in brainwave patterns, blood oxygen saturation and breathing patterns. One or more of the individual's EEG, EOG, EMG, position, breathing and blood oxygen levels can be monitored by a monitor unit associated with the CPAP device. In some instances, the monitoring unit may be part of the CPAP device. The EEG is used to observe brain activities during sleep. The EMG is used to observe muscle tone during sleep. The EOG is used to observe eye movement during sleep. The three physiological signals (i.e. EEG, EOG, and EMG) may be used together to score sleep stages.
Arousals due to upper airway resistance may be detected from a shift in frequency of the patient's EEG and/or EOG as well as a decrease in blood oxygen levels. The monitoring unit includes an algorithm that detects the arousals and sleep stages, and uses the physiological information to automatically adjust the delivered respiratory gas pressure to the CPAP device wearer based on the physiological information. The algorithm can also use the physiological information to determine the effectiveness of the treatment.
In order to measure the physiological information, various sensors are attached to the CPAP patient. For instance, to measure EEG, EOG and EMG, several electrodes may be applied to the patient's head and face. To measure blood oxygen level, a blood oximetry probe may be applied to the patient's finger or earlobe. To measure body position, an accelerometer-based sensor may be placed on the patient's chest. These sensors are connected to the monitoring unit with appropriate electrical wires. Once the sensors are applied, the CPAP device wearer puts on the mask assembly. The mask assembly includes a nasal mask (or a nasal/oral mask) and a harness that maintains the position of the nasal mask on the face of the wearer.
However, the application of electrodes by the CPAP device wearer is not an easy process; it is difficult, time consuming and prone to errors. The process involves preparing the site to reduce impedance, attaching one electrode at a time with tape and/or adhesives, and then individually wiring each electrode to the monitoring unit. In a clinical setting, the electrodes are typically positioned by a polysomnography technician according to standard positions, or as directed by a physician. In a non-clinical setting, such as at a patient's home, the patient or another untrained person may be required to position the electrodes on the patient. Such untrained persons may have difficulty placing the electrodes in the correct location or correctly wiring the electrode to the monitoring unit. Even in a clinical setting, a trained technician may position an electrode incorrectly.
Furthermore, once the electrodes and the other sensors are applied to the wearer and connected to the monitoring unit, the arrangement results in many wires emanating from different locations on the wearer to the monitoring unit. As a result, the arrangement is uncomfortable for the wearer and interferes with the wearer's natural movements, which makes it difficult for the wearer to sleep. Consequently, the wearer may find it difficult to find a comfortable sleep position. In addition, the wearer may move during sleep such that the sensors become disconnected from the monitoring unit. Also, motion of the wires connecting the electrodes to the monitoring unit introduces electrical artifacts that hides the underlying physiological information. These technical difficulties also prevent sleep studies from being conducted at a patient's home. Further, the unfamiliar environment in the sleep lab may dramatically affect the patient's sleep which in turn may lead to an inaccurate diagnosis.
It is desired to address or ameliorate one or more of the shortcomings, disadvantages or problems associated with prior systems or devices, or to at least provide a useful alternative thereto.